1. Field of the Invention
The present invention relates to a sample temperature control method, and more specifically relates to a method of temperature control in a plasma processing apparatus.
2. Description of the Related Art
FIG. 18 is a diagram illustrating a conventional method of adjusting sample temperatures. As shown in FIG. 18, a sample is placed on a sample stage 10 cooled by a refrigerant. The sample stage has an embedded heater 13 and is configured to regulate an amount of heat by regulating the electric power to be supplied to the heater 13. Furthermore, the sample stage has an embedded temperature sensor 15 capable of measuring a temperature of the sample stage 10 (refer to Japanese Unexamined Patent Application Publication No. 2005-522051 and its corresponding U.S. Pat. No. 6,921,724).
FIG. 19 is a diagram illustrating a conventional temperature control apparatus. As shown in drawing, the apparatus employs a feedback control method for electric power u1 to be supplied to the heater so that measurement value y1 of the temperature sensor becomes a target value r. Also, the PI control is commonly used as a feedback control method. In recent years, a structure wherein the sample stage is divided into three regions: center, edge, and middle, each having a heater and a temperature sensor has been realized.